The field of orthodontics relates to the supervision, guidance and correction of teeth towards proper positions in the oral cavity. Orthodontic therapy generally involves the application of forces to move teeth into a proper bite configuration, or occlusion. One mode of therapy, known as fixed appliance treatment, is carried out using a set of tiny slotted appliances called brackets, which are affixed to at least the anterior, cuspid, and bicuspid teeth of a patient. In the beginning of treatment, a resilient orthodontic appliance known as an archwire is received in each of the bracket slots. The end sections of the archwire are typically anchored in appliances called buccal tubes, which are affixed to the patient's molar teeth.
When initially installed in the brackets and buccal tubes, the archwire is deflected from its original arcuate (or curved) shape, but then gradually returns to this shape during treatment. In this. manner, the archwire applies gentle, therapeutic forces to move the teeth from improper positions to proper positions. Taken together, the brackets, buccal tubes, and archwire are commonly referred to as “braces”. Braces are often prescribed to improve dental and facial aesthetics, bite function and dental hygiene. In many instances, a set of brackets, buccal tubes and an archwire is provided for each of the upper and lower dental arches.
Brackets and other components of the fixed appliance system are commonly placed on the labial (i.e., near the patient's lips and cheeks) surfaces of the teeth. In recent decades, advances in the art have enabled brackets to be placed on the lingual surfaces of teeth. Accordingly, the components of the fixed appliance system, including the archwire, are disposed nearer the tongue, providing an attractive, aesthetic alternative as the appliance system is essentially hidden from view. Lingual brackets often have a customized design individually for every tooth and patient because, other than the labial surfaces of a tooth, the lingual surfaces greatly vary in shape relative to each other so that a “one size fits all” bracket shape typically cannot be used. Exemplary appliance systems that include brackets customized to the lingual surfaces of a dental arch are disclosed in U.S. Pat. No. 7,811,087 (Wiechmann et al.).
During certain stages of treatment, additional intraoral appliances may be prescribed for use in conjunction with fixed appliances to correct particular kinds of malocclusions. For example, some appliances are used to correct Class II malocclusions, such as an overbite where the mandibular first molars are located excessively distal (in the rearward direction) with respect to the maxillary first molars when the jaws are closed. Other appliances remedy an opposite malocclusion, known as a Class III malocclusion, such as an underbite where mandibular first molars are located excessively mesial (in the forward direction) with respect to the maxillary first molars when the jaws are closed.
In recent years, Class II and Class III correctors have been developed that are installed by the orthodontist and require minimal patient intervention during the course of treatment. These devices advantageously correct Class II and Class III malocclusions without need for patient compliance as with prior common head gear. A number of intra-oral devices for correcting Class II and Class III malocclusions are known in the art. For example, U.S. Pat. Nos. 4,708,646, 5,352,116, 5,435,721, 5,651,672, 5,964,588 and 8,257,080 describe intra-oral bite correctors with flexible and/or telescoping members that are connected to upper and lower arches of a patient. A bias tends to urge the members toward a normally straight orientation and provide a force that pushes one dental arch forward or rearward relative to the other dental arch when the jaws are closed.
As the position of the jaws is corrected, that bias is reduced during jaw closure and consequently provides less force in compression. In response, the practitioner may elect to increase the effective, active length of the intra oral device to ensure that the force exerted on the patient's jaws remains effective during the course of treatment. The effective length is typically increased or otherwise modified by removing the intra-oral device from the patient's mouth and then changing the components to continue treatment. Alternatively, stops or collars can be added to such devices to reduce the length of travel and increase the active force supplied.
Moreover, there are various possibilities in connecting these devices to the dental arch. Banded headgear tubes are still commonly used to provide a distal connection to the upper dental arch. These banded appliances, however, are not universally beloved. Bondable molar appliances are more convenient to use with labial systems in many respects and some orthodontists prefer them over banded appliances. As another option, connection to the dental arch may be made indirectly by coupling the intraoral device to one or both archwires.